I can’t quite wrap my head around the legality of it and under whose legal jurisdiction it falls, but the Principality of Sealand is a micronation off the southeastern coast of England. It has coins and stamps and up until 1997 had passports. The problem was, someone started forging them and about 150,000 of them appeared in China during the transition of Hong Kong, so all passports were revoked. Apparently, it also has license plates, which I find odd because Sealand is a 550 square metre former naval fort.
Since 1967, Sealand has belonged to no sovereign nation, with the UK having given up all claim to it and by virtue of it being in international waters. However, no sovereign state recognizes it as sovereign, so I have no idea what that makes it. Other than a former naval fort some people used to live on.
I don’t really know how to write about Sealand, so I’ll just quit while I’m ahead and leave you with some reading.